Current Biochemical Engineering (Discontinued) - Volume 2, Issue 2, 2015

Membrane distillation is a relatively new process alternative to conventional separation methods like distillation and reverse osmosis concerning cost and energy saving technology. Membrane distillation is beneficial over other separation techniques in terms of theoretical rejection of ions, macromolecules, colloids, cells and other nonvolatile compounds and also lowers operating temperature and pressure making it more advantageous for thermally sensitive solutions. The cost of the process is reduced considerably compared to conventional distillation because of reduced vapor space. In contrast, there are some limitations of MD. The major limitation being the definition of the phenomenon: the process requires an aqueous solution, and it should be dilute so that wetting of hydrophobic membranes is avoided. This limits membrane distillation to applications such as desalination (currently dominated by reverse osmosis), removal of trace volatile organic compounds from waste water, and concentration of ionic, Colloidal, or other relatively Non-volatile aqueous solutions. Membranes have always been an integral part of downstream processing. The present review summarizes the state of the art of Membrane distillation and osmotic membrane distillation process in downstream processing with importance to the work done after the year 2008.The review also covers the necessary techniques needed for characterization membranes used in MD.

Endophytes are the microorganisms that occur within the tissues of the plants without causing any noticeable symptoms and diseases to the host. In general, fungi and bacteria are the most common microbes exist as endophytes in plants. In recent years, endophytic fungi are known to produce several bioactive secondary metabolites, mainly used in pharmaceutical, agricultural and industrial applications. This review describes the isolation of naturally occurring bioactive compounds from endophytic microorganisms. In the recent past, a wealth of information on the isolation and purification of bioactive secondary metabolites from various endophytes have been reported. As endophytes produce these secondary metabolites in lower concentrations, it is required to employ improved isolation and purification methods of these secondary metabolites for their complete recovery.

The aim of this review paper is to highlight the recent developments in downstream processing of biomolecules using reverse micellar extraction (RME) technique. Reverse micelles (RMs) are a nanometer size aggregation of surfactant molecules in organic solvents. The inner core of RMs contains an aqueous phase, which can solubilize biomolecules such as amino acids, proteins, enzymes, and DNA. RME is a two-step purification technique, which involves solubilization of biomolecule into RMs (forward extraction) and recovery of these biomolecules from RMs to fresh stripping phase (back-extraction). Solubilization and the recovery of biomolecules are possible by altering processing parameters like pH of aqueous phase, type of salt, ionic strength, type of organic solvent, surfactant type, phase contact time, operating temperature and size of RMs. The importance of these processing conditions has been discussed in detail in this review. Mathematical modeling of mass transfer in RME is also covered. This review highlights the application of RME in biomolecule purification from the natural source, nanoparticle synthesis, refolding of proteins and selective separation of biomolecules from a mixture. Apart from this, we have also discussed about the integration of RME with other downstream processing (DSP) techniques, recent developments in innovative cost effective RME technique, recycling of RME components and future prospects for RME.

Use of conventional organic solvents in an extraction brings problems such as toxicity, volatility, flammability and denaturization of biomolecules. In contrast, Ionic liquids, which are called as green solvents, are composed completely of ions and devoid of these problems. Traditional organic solvents have been replaced by Ionic liquids in many industrial applications such as organic synthesis, catalysis, extraction (liquid phase micro-extraction, solid phase micro-extraction and liquid-liquid extraction), adsorption, chromatography (mobile phase additives) and supported liquid membranes. Even though, the applications of ionic liquids in bioseparations are in their early stages, the academic interest in ionic liquids is in the rise. The major applications of ionic liquids in separation technology are presented in this present review paper. Furthermore, the future scenario of the ionic liquids in separation techniques is discussed.

Improved bioseparation techniques are increasingly important for biotechnology because downstream processing accounts for a major share of the production cost. Several processes do not become commercially feasible for this reason involved in the purification protocols (50-90% of the final product cost). Downstream processing poses several problems mainly because of two reasons (1). Target biomolecule or compound is generally present in dilute form and (2). It is present along with several other undesired compounds, needing a chain of purification steps to obtain the desired product in the required purity as well as concentration. Hence there is a need for efficient and economically feasible downstream processing methods. Aqueous Two Phase Extraction is one such method which offers several advantages such as biocompatibility (due to presence of high water content), ease of scale-up and scope for continuous operation. In ATPE, equipment used in the conventional organic extraction in the chemical industry (e.g., spray, packed column, etc.) can be adapted easily when multistage procedure is needed and the phase separation is achieved in these contactors by gravity separation, thereby eliminating the need of expensive equipments. In spite of having so many advantages, ATPE method did not realize the wide commercial adoption that it richly deserves, due to several factors. In the present review, special emphasis is given to different equipments employed for ATPE both at large and lab scales, besides attempting analysis of equipment design parameters of these equipments along with operational conditions that affect their performance. This review also attempts to present major advantages and challenges faced for the industrial adoption of the technique.

Coconut, a tropical fruit, is a well-known source of drink, food and oil as well. Numerous unprocessed, semiprocessed and processed coconut products have entered the global markets in small and big quantities. In the coconut industry, downstream processing plays vital role as the different products obtained are a result of different unit operations such as extraction, concentration and drying. Products like copra, coconut oil and desiccated coconut have a growing demand along with stringent quality specifications when exported to non-producing countries. These demands can be met only by large scale production using advanced technologies in drying and/or expelling under hygienic conditions and improvised packaging. Value added products such as nata-de-coco, coconut vinegar, toddy, etc. are being produced using microorganisms for bioconversion using coconut as a raw material. Aqueous processing and enzymatic treatment can favor the extraction of coconut oil in environmentally safe and economical manner, also yielding an edible protein product. Diversification of coconut derived products and value addition could only help the coconut growers in getting remunerative returns for the produce. This article aims to review coconut processing and related issues with special emphasis on bioprocessing and bioprocess engineering which have revolutionised the scale at which value added coconut products can be manufactured.

In recent years, pursuit for novel techniques for the extraction of bioactive compounds from natural sources has gained the attention of many researchers. Various conventional solid-liquid and liquid-liquid extraction methods and non-conventional technologies such as microwave and ultrasound assisted extraction, supercritical fluid extraction, pulse-electric field assisted extraction, enzyme assisted extraction etc. has been explored well in this area. This review aims at providing an extensive overview of general aspects of various natural bioactive compounds and different techniques and mechanism for the extraction of these compounds. Scope of the proposed topic: It is vital for the pharmaceuticals, food, cosmetic and chemical industries to be aware with latest technology choices and researches aimed at enhancing the yield and quality of bioactive compounds. The paper aims to discuss various techniques employed for concentration and purification of bioactive compounds and highlights the changes in extraction conditions to enhance the yield and quality of bioactive compounds so as to exploit them for human good.

The increasing use of antibodies in various biotechnological and pharmaceutical applications has pushed demand to produce antibodies in larger quantities. Considerable interest has now focused on reducing manufacturing costs and reorganizing process development activities to facilitate commercialization. Hence, there is an absolute requirement for purification techniques that meet the stringent quality requirements of these therapeutic agents. Presently, a select combination of techniques are applied to purify antibodies, of which, the most frequent are salting out, affinity chromatography and ion exchange chromatography. Of these, affinity chromatography is increasingly being used as a first step in the purification of antibodies due to its high specificity. In the current review, we focus on the potential of various affinity chromatography practices with an emphasis on their power and limitations.